NETGEAR FVS318 - ProSafe VPN Firewall Router Reference Manual page 209

Reference Manual for the Model FVS318 Broadband ProSafe VPN Firewall
Internet Control Message Protocol
ICMP is an extension to the Internet Protocol (IP) that supports packets containing error, control, and
informational messages. The PING command, for example, uses ICMP to test an Internet connection.
Internet Protocol
The method or protocol by which data is sent from one computer to another on the Internet. Each computer
(known as a host) on the Internet has at least one IP address that uniquely identifies it among all other
computers on the Internet. When you send or receive data (for example, an e-mail note or a Web page), the
message gets divided into little chunks called packets. Each of these packets contains both the sender's
Internet address and the receiver's address. Any packet is sent first to a gateway computer that understands a
small part of the Internet. The gateway computer reads the destination address and forwards the packet to an
adjacent gateway that in turn reads the destination address and so forth across the Internet until one gateway
recognizes the packet as belonging to a computer within its immediate neighborhood or domain. That
gateway then forwards the packet directly to the computer whose address is specified.
Because a message is divided into a number of packets, each packet can, if necessary, be sent by a different
route across the Internet. Packets can arrive in a different order than they were sent. The Internet Protocol
just delivers them. It's up to another protocol, the Transmission Control Protocol (TCP) to put them back in
the right order. IP is a connectionless protocol, which means that there is no continuing connection between
the end points that are communicating. Each packet that travels through the Internet is treated as an
independent unit of data without any relation to any other unit of data. (The reason the packets do get put in
the right order is because of TCP, the connection-oriented protocol that keeps track of the packet sequence in
a message.) In the Open Systems Interconnection (OSI) communication model, IP is in Layer 3, the
Networking Layer. The most widely used version of IP today is IP version 4 (IPv4). However, IP version 6
(IPv6) is also beginning to be supported. IPv6 provides for much longer addresses and therefore for the
possibility of many more Internet users. IPv6 includes the capabilities of IPv4 and any server that can
support IPv6 packets can also support IPv4 packets.
IP
See "Internet Protocol" on page 7.
IP Address
A four-byte number uniquely defining each host on the Internet, usually written in dotted-decimal notation
with periods separating the bytes (for example, 134.177.244.57). Ranges of addresses are assigned by
Internic, an organization formed for this purpose.
IPSec
Internet Protocol Security. IPSec is a series of guidelines for securing private information transmitted over
public networks. IPSec is a VPN method providing a higher level of security than PPTP.
IPX
Short for Internetwork Packet Exchange, a networking protocol used by the Novell NetWare operating
systems.
Like UDP/IP, IPX is a datagram protocol used for connectionless communications. Higher-level protocols,
such as SPX and NCP, are used for additional error recovery services.
Glossary
7
M-10146-01